1. FIELD OF THE INVENTION:
This invention relates to the art of clamping devices especially adapted for use with lifting and transporting equipment to automatically clamp onto drums with peripheral "L" chime rings, lift the drums, and to then automatically release the drums as they are deposited at a desired location. The invention specifically deals with drum clamping units for use with molded plastic drums having "L" shaped peripheral chime rings spaced below the heads of the drums.
2. THE PRIOR ART:
Drum clamping and lifting equipment for a single drum or a cluster of drums is generally known in the art from the teachings of the Ericson U.S. Pat. No. 3,338,616 and the Lund and Ericson U.S. Pat. No. 3,718,228. The teachings of these patents are directed to devices for clamping and lifting conventional drums with raised steel rims around the drum heads. These devices were triggered by engagement with these rims to swing a top jaw over the drum head against the inner periphery of the rim and to lift a bottom jaw along the periphery of the drum to engage the bottom of the rim. The rim on the drum head had to be a strong and rigid projection unimpeded both radially and axially to receive the jaws and the trigger mechanism. Since the rims were restricted to the diameter of the drum head, the jaws had to be narrow to grip the rim without deforming it.
This equipment was useless for lifting the now popular lightweight molded plastic drums which have peripheral chime rings below the drum heads. These chime rings are "L" shape in cross section and surround the drum peripheries so that while they are radially impeded they also have a larger diameter than the drum and can accept wider jaws.
It would therefore be an improvement in this art to provide drum clamping units adapted to be suspended from drum lifting and conveying equipment, such as fork trucks, cranes, and the like, which will align itself alongside a single drum or between a ring cluster or nest of drums as it is being lowered, will automatically trigger clamping jaws into clamping positions as it engages the drum heads, will latch the jaws onto peripheral "L" shaped chime rings of the drums as it is raised and will then automatically release the drums when they are again lowered onto a support surface. The jaws are held in retracted positions after releasing the drums and are automatically extended into gripping positions when the trigger mechanism again engages the heads of the next group of drums.
It would especially be an improvement in this art to provide automatic drum clamping equipment for molded plastic drums having peripheral chime rings of "L" shape cross section spaced below the drum heads.